The PING command is a network diagnostic tool used to test the reachability of a host on an Internet Protocol (IP) network. It sends a small packet of data to the target host and waits for a response, measuring the round-trip time for data packets to travel from the source to the destination and back.
*How PING Works*
1. *Sending ICMP Echo Request*: PING sends an ICMP Echo Request packet to the target host. 2. *Waiting for Response*: The target host responds with an ICMP Echo Reply packet if it is reachable. 3. *Measuring Round-Trip Time*: PING measures the time it takes for the packet to travel from the source to the destination and back.
*Common Uses of PING*
- *Network Troubleshooting*: Identify connectivity issues between devices on a network. - *Latency Measurement*: Measure the round-trip time for packets to travel between devices. - *Packet Loss Testing*: Detect packet loss during transmission.
*PING Command Options*
- *`-t`*: Continuous ping until manually stopped (Windows). - *`-n`*: Specify the number of pings to send (Windows). - *`-c`*: Specify the number of pings to send (Linux/macOS). - *`-i`*: Set the interval between pings (Linux/macOS). - *`-w`*: Set the timeout for pings (Windows). - *`-4`* and *`-6`*: Force IPv4 or IPv6 packets, respectively.
*Common PING Error Messages*
- *"Request timed out"*: No response received from the target host within the default time period. - *"Destination host unreachable"*: No route to the target host. - *"General failure"*: Problem with the local network adapter or configuration.
*Tips and Best Practices*
- Use PING to test connectivity to multiple hosts to isolate network issues. - Use continuous ping to monitor network changes and detect issues. - Analyze PING output to identify packet loss, latency, and other network issues ¹ ².
00:00Hello everyone. In this video we're going to talk about one of the most widely used
00:05utilities that's used in networking and I'm talking about the ping command. Now
00:10the ping command is a simple tool that you can use to troubleshoot networking
00:15issues such as network connectivity. So you can use it to test if you're
00:19connected to a local area network or if you're even connected to the internet.
00:24You can also use it to test if your network interface card is working
00:29correctly and it's also used to test DNS issues such as name resolution. So for
00:36example let's go ahead and ping an IP address of a host. Now this host could be
00:41any network device such as a computer, server, router, or printer, whether it's
00:47on your local area network or over the internet. But in this example we're going
00:52to ping a server in our local area network. So we would open up a command prompt and
00:57then we would type the word ping along with the IP address of the server and
01:02then press enter. Then the ping utility will send out four data packets to the
01:07IP address of the server. Then our computer will wait for a response. Then the server
01:13will send the data packets back to us as a reply. And these replies are called
01:18echo reply requests. And these replies inform you about what's happening with the
01:24server we pinged. So for example if we received a reply then that is a good sign.
01:29Then that means that there is network connectivity between us and the server.
01:34Whether that server is on your local area network or over the internet. So four
01:40packets were sent and in four packets were received. But if we pinged the same
01:46server and this time if we didn't get a reply then that means that the server
01:51didn't reply back. And it could mean that there is no network connectivity between
01:55our computer and the server. Now this could be for several different reasons.
02:00So for example when we ping the server and if we got a message back that says
02:05request timed out then that could mean that the server is powered down. Or it could
02:11also mean that the server is up and running but it's using a firewall that's
02:15blocking all ping requests.
02:21Now what happens when you try and ping a host and not all of the data packets reply
02:27back to you. So for example when you ping a host your computer sends out four data
02:33packets. But sometimes you may only get one, two, or three packets back instead of
02:39the four that you sent out. Well this is called packet loss. And packet loss can occur
02:44for several reasons. It could mean that there's network congestion. If there is a lot of
02:50traffic on a network and the network can't handle all that extra traffic then data
02:55packets will get dropped. Or it could also happen because of faulty hardware such as
03:00bad cables or bad wiring. Or it could be a bad network card or bad connections. Or it
03:08could be a bad modem which is exactly what happened to me in my case. A few years ago I
03:13was constantly lagging in just about everything I did on the internet. So I
03:18did a continuous ping test and I was dropping at least one third of my
03:23packets fairly consistently. So I determined that it had to be my modem. So I had it
03:29replaced and it solved the problem.
03:33Or in another scenario if we wanted to ping a remote server on the internet and if we
03:39got a message that says destination host unreachable then that means that a route
03:44to the destination cannot be found. So it could mean that a router doesn't have
03:49any information on how to route data to the destination. Or it could also mean
03:55that the remote server is down or disconnected from the network. Or it could
04:00also mean that your computer is not connected to a network. So let's use the
04:05ping command in a typical scenario. So suppose someone tells me that they
04:09don't have an internet connection because they can't access any web pages
04:14with their computer. Which is a pretty common issue. So the first thing I do is
04:19that I would sit at their computer and use the ping utility to see if in fact they
04:24are not connected to the internet. So even before I check their modem or router or
04:30any cable connections the first thing I do is do a simple ping test. So I would
04:36open up a command prompt and see if I can ping a website such as yahoo.com. Now
04:42notice in this method I'm actually pinging the domain name yahoo.com and not
04:48its IP address. Because by doing it this way I'm also testing name resolution
04:54issues related to DNS. And also besides that I don't have Yahoo's IP address
05:00memorized. So by pinging yahoo.com and if the ping is successful then I know that
05:07we are connected to the internet. Because when I got a successful reply from yahoo.com
05:13then I automatically know that all of my hardware such as my cables, the network
05:19card, the router, and the modem are all working correctly. Including my internet
05:25service provider. So now I know that the reason that this computer can't bring up
05:30web pages is related to software and not hardware. So the problem is most
05:36likely with their internet browser or it's a firewall issue. So by doing a ping
05:43test first it saved me a lot of time. Because I bypassed the hassle of looking
05:48around for the modem or the router. Or looking at LEDs or checking the cables.
05:53Or looking behind the computer to see if the network cable is plugged into my
05:58network card. I simply sat down and did a simple ping test. So really the only time
06:04you need to check your hardware is if the ping was not successful. However even
06:09before you start checking hardware you can also use the ping command to check
06:13other things. Such as testing if your network interface card is working
06:17correctly. And this is called a loopback test. A loopback test will send out
06:22signals back to your computer for testing purposes. So at a command prompt I would
06:28type ping and then the loopback IP address which is 127.0.0.1. Or you can
06:35simply type ping localhost which does the same thing. And if the ping was
06:40successful then you can be assured that your network card is working properly. But if
06:46the loopback test failed then there's a problem with your network card. Now the
06:51ping command can also be used to test DNS name resolution issues. And if you're not
06:56familiar with what DNS does, please watch my DNS video on my YouTube channel. But in a
07:02nutshell, DNS is what resolves domain names to IP addresses. So as you recall earlier I
07:08did a ping test by pinging the domain name yahoo.com instead of its IP address. And as
07:15I said before if the ping was successful then that means that all of my hardware is
07:20working correctly. But in addition it also verifies that DNS is working correctly. So
07:26as you can see DNS successfully resolved and found the IP address for yahoo.com. But if we pinged yahoo.com and we got a message that says ping request
07:37could not find host yahoo.com please check the name and try again, then this
07:43could be a DNS issue. Because our computer could not resolve the domain name to an IP
07:49address. So the next thing to do is to try and ping the IP address instead and that's
07:54if you already knew what the IP address was already. Or if you don't, like most of
07:59us don't already, you can type in an easy IP address to remember. Such as Google's DNS
08:05IP address which is 8.8.8.8.8. And if the ping was successful this time then this
08:13confirms it's a DNS issue. Because the computer can ping IP addresses but it
08:19can't ping domain names. So to solve this you can try a few things. You can try
08:24flushing your DNS by typing ipconfig forward slash flush DNS at a command prompt. Or you
08:31may want to check your DNS settings on your network card configuration. And it
08:36could also be a problem with the DNS servers themselves. Or it could be a
08:40problem with your internet service provider. And finally the ping command can
08:45also be combined with other sub commands called switches. And switches are used to
08:51alter the parameters of the ping utility. And you can view a full list of these
08:56switches by typing ping forward slash and then a question mark. So thank you all
09:02for watching this video. Please subscribe and I'll see you in the next video.
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